What are coding regions of eukaryotic mRNA that are translated?
A. exons
B. histones
C. caps
D. introns
The Correct Answer and Explanation is:
The correct answer is A. exons.
In eukaryotic cells, the process of gene expression involves transcription and translation, where the genetic code in DNA is first transcribed into messenger RNA (mRNA), which then directs the synthesis of proteins. Within the mRNA molecule, there are specific segments known as exons, which are the coding regions that ultimately get translated into protein.
Explanation:
- Exons: Exons are the portions of a gene that are retained in the mature mRNA after the initial transcription. During mRNA processing, introns (non-coding regions) are spliced out, leaving only the exons. Each exon contains codons, which are sequences of three nucleotides that correspond to specific amino acids in the protein being synthesized. The arrangement and sequence of exons dictate the order of amino acids in the protein, which ultimately determines the protein’s structure and function.
- Introns: In contrast to exons, introns are non-coding regions of the gene that are transcribed into pre-mRNA but are removed during the splicing process. They do not contribute to the final protein product and are considered “interruptions” in the coding sequence.
- Histones: Histones are proteins that play a crucial role in packaging DNA into chromatin but are not related to the coding regions of mRNA. They help to regulate gene expression but are not themselves part of the mRNA.
- Caps: The 5′ cap of eukaryotic mRNA is a modified guanine nucleotide added to the beginning of the mRNA molecule. While it is essential for mRNA stability, nuclear export, and initiation of translation, it is not a coding region.
In summary, exons are the coding sequences within eukaryotic mRNA that are ultimately translated into proteins, while introns, caps, and histones play different roles in gene expression and cellular function.